Local Excision for Rectal Cancer: An Uncertain Future

Local Excision for Rectal Cancer: An Uncertain Future

Drs. Weber and Petrelli review much of the literature regarding
patient outcomes after local excision alone, as well as local
excision plus chemoradiotherapy, in patients with various stages of
low rectal adenocarcinoma. The authors apparently were unaware that
the Radiation Therapy Oncology Group (RTOG) experience with local
excision plus chemoradiation, which antedated the Cancer and Leukemia
Group B (CALGB) study, will soon be in print to provide further
multi-institutional support for these methods along with much greater
follow-up. They also omitted our long-term data (median follow-up of
survivors is 67 months) showing the very low locoregional recurrence
rates in patients with T2 cancers treated by local excision and chemoradiotherapy.[1]

The authors correctly emphasize the conundrum resulting from the
unresected (and thus unexamined) regional lymph nodes in patients
with low rectal cancer. Some patients will have positive nodes even
if they have a T1 cancer, and thus surgical excision alone will be
doomed to failure. Many more patients with T2 and T3 cancers will
have positive nodes; we have no specific information about whether
these nodes will be controlled by chemoradiotherapy.

Since reported recurrence rates after local excision and
chemoradiotherapy are considerably lower than percentages of nodal
positivity reported from large series of patients with radical rectal
and mesorectal excision, it is likely that chemoradiotherapy will
control those metastases in at least some, and probably many, of
these patients.[1-5] Perhaps the major problem with the technique is
that we cannot identify patients with positive nodes, and, thus, we
cannot provide adjuvant chemotherapy to those who should be receiving it.

Weber and Petrelli conclude that local excision has not been proven
to be as effective as radical rectal excision, nor has postexcisional
chemoradiotherapy been proven to be superior to excision alone. The
former comparison will, undoubtedly, never be subjected to the
scrutiny of a phase III trial. However, there are enough phase II
studies of local excision of T1 tumors with low-risk histology to
indicate that local excision is equivalent to abdominoperineal
excision and certainly has less toxicity.

The latter comparison also probably will never be tested in a
randomized trial because it is highly unlikely that most patients
with a T2 cancer will be as well served by local excisional surgery
alone as they would by combined-modality therapy. The authors point
to a statement taken out of context from an article by Willett et al
as indicating that there is no difference between these therapies.[6]
However, the groups compared in this study were by no means
equivalent. (Those with deeper and less differentiated lesions were
given chemoradiotherapy.)

Identifying Positive Lymph Nodes

Ideally, carcinoembryonic antigen-labeled radioantibodies could be
administered to the patient prior to any manipulation of the tumor
(other than transrectal ultrasound), and any "hot" nodes
identified in the mesorectum could either be biopsied or assumed to
contain cancer and be given appropriate treatment, such as
abdominoperineal resection or very low anterior resection with total
mesorectal excision. Patients who are unable or unwilling to undergo
major surgery could theoretically have full-thickness transanal
excision followed by chemoradiotherapy and 6 months of systemic
chemotherapy. However, it is unlikely that available radioantibodies
can provide high enough target-to-background activity to be
recognized by currently available radiodetection devices.

Perhaps sentinel node technology could identify positive nodes in
these patients, but this would probably involve at least
transcoccygeal approaches, which, in turn, might jeopardize
curability by radical excision should positive lymph nodes be found.

Treatment Recommendations

In the absence of such technology, we believe that patients with T1
lesions and high-risk histology (poor differentiation, lymphovascular
invasion) should receive chemoradiotherapy or radical excision, and
those with T2 lesions and high-risk histology should receive both
chemoradiotherapy and post-radiation adjuvant chemotherapy or radical
excision. All patients with T2 lesions should be treated with
chemoradiotherapy after local excision. Patients with involved
margins or margins within 1 to 2 mm of the cancer should either
undergo transanal re-excision for wider margins, or radical resection
with total mesorectal excision and coloanal anastomosis or
abdominoperineal resection.

There are simply too few reported patients with T3 cancers who have
had local excision plus chemoradiotherapy to be able to definitively
evaluate the procedure, although most available reports suggest that
great caution should be exercised. If we had an effective method to
determine regional nodal positivity in these patients and were able
to provide wide margins around the tumors (small tumors, minimal
mural penetration), a trial of local excision plus chemoradiotherapy
plus adjuvant chemotherapy would seem to be a logical course of
action. Without such a method to detect involved lymph nodes,
however, only patients who are unable or unwilling to undergo major
rectal surgery should be offered such therapy, and then only after
transrectal ultrasound has demonstrated no enlarged lymph nodes.

Salvage Therapy for Locoregional Recurrence After Local Excision

Finally, to add to the scant information provided about salvage
therapy for patients with locoregional recurrence after local
excision, we should point to our review, and provide slightly more
information on the six patients whom we have treated.[7] Two died of
distant metastases 6 and 30 months following radical resection, while
four remain alive (three of whom are free of recurrence 41, 72, and
83 months after resection of the locoregional recurrence, and one of
whom developed pelvic and lung recurrences 81 months after resection
of the recurrence).